body, a Gastrula. The cuts on the left page represent the de- 

 velopment of an Amoeba, a unicellular animal which remains so 

 all its life, but propagates by fission. The two last cuts on the 

 left page show an animal now living in the North Sea, Mago- 

 sphaera planula. It never gets beyond this stage, which corre- 

 sponds to the hollow ball stage of the corals. The last cut on 

 the left page shows another animal now living, bisected. It is 

 Peinmatodiscus gastrulaceus. Haeckel regards these living forms, 

 Amoeba Magosphaera, and Pemmatodiscus, as present-day type* 

 of the primeval development of the animal world. 



135 



